1. Field of the Invention
The present invention relates to a swivel arrangement for a chair seat that provides improved sitting comfort and safety and easier operation and assembly.
2. Description of the Related Art
A typical chair is shown in FIGS. 10 and 11 and includes a backrest 1', a chair seat 2', a chassis 3', a pneumatic rod 4', and a base 5'. A lower end of the backrest 1' is connected to the chair seat 2'. The chassis 3' includes a swivel seat 31', a connecting seat 32', a spring seat 33', an adjusting rod 34', and a connecting rod 35'. The swivel seat 31' includes a number of holes 311' in corner areas thereof for connection with the chair seat 2', a hole 312' in a mediate portion thereof for connection with the spring seat 33', and lateral holes 313' and 314' through which the adjusting rod 34' and the connecting rod 35 extend, respectively. The connecting seat 32' includes a hole 321' through which the pneumatic rod 4' extends. The connecting seat 32' further includes lateral holes 322' and 323' through which the adjusting rod 34' and the connecting rod 35 extend, respectively. The connecting seat 32' further includes a hole 324' for mounting the spring seat 33'. The spring seat 33' includes a sleeve 332', a spring 331' partially mounted in the sleeve 332', and a threaded rod 333' that extends through the hole 312' in the swivel seat 31' and securely engages with a lower end of the sleeve 332'. The adjusting rod 34' includes an end 341' extended through the lateral hole 313' to restrain swivel movement of the swivel seat 31'. The adjusting rod 34' further includes a pressing section 342' to press against an upper end of the pneumatic rod 4' to adjust the level of the chair seat 2'.
Although the seat 2' and the backrest 1' can be swiveled due to provision of the spring 331', the inclination angle of the backrest 1' relative to the seat 2' cannot be fixed. In addition, as shown in FIG. 12, the user might fall from the chair when the rearward motion of the backrest 1' goes too far, since the seat 2' swivels together with the backrest 1'.
FIG. 13 of the drawings illustrates another conventional chair that includes a backrest 6' that is connected to a movable seat 62' via a connection rod 61'. The movable seat 62' is connected to a chassis 7' that includes an elastic means 71' to allow back-and-forth swivel motion of the backrest 6'. The chair seat 8' and the backrest 6' are secured together to provide improved sitting stability and safety. Two control rods (not labeled) are attached to the chassis 7' to respectively control the level of the backrest 6' and swivel motion of the backrest 6'. Nevertheless, the chair seat 8' is thoroughly fixed and thus provides less sitting comfort. In addition, two control rods are required to control the level and inclination angle of the backrest 6' and thus result in inconvenient operation to the user and inconvenient assembly.